Elevator system

ABSTRACT

A dispatching control for elevators in which traffic is measured in terms of door open time for cars traveling between the terminals. The door open time of up traveling cars is balanced against the door open time of down traveling cars for a comparison time interval, and, if there is an unbalance of door open time, the terminal time at one terminal is adjusted to maintain substantially even car spacing.

United States Patent Inventors Alan M. Hallene [56] References Cited Mflline; UNITED STATES PATENTS App] No gf 'g 2,759,564 8/1956 Borden .5 187/29 l Filed Oct-16,1967 3,353,631 11/1967 Burgy 187/29 Patented June 29, 1971 Primary Examiner-D. Dobeck Assignee Montgomery Elevator Company Assistant Examiner-W. E. Duncanson, Jr.

Continuation of application Ser, No, AllorneyHofgren, Wegner, Allen, Stellman and MCCOld 265,239, Mar. 14, 1963, now abandoned.

ABSTRACT; A dispatching control for elevators in which traffic is measured in terms of door open time for cars travelgg i g i ing between the terminals. The door open time of up traveling rawmg cars is balanced against the door open time of down traveling US. Cl 187/29 cars for a comparison time interval, and, if there is an un- Int. Cl. 1366b 1/20 balance of door open time, the terminal time at one terminal is Field of Search 187/29 adjusted to maintain substantially even car spacing.

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This invention relates to an automatic elevator system, and in particular it relates to a control system for operatorless elevators which shifts automatically between various modes of operation in accordance with traffic demands upon the system and the internal condition of the system.

Much of the developmental work in the elevator industry in recent years has been directed to improved automatic elevator control systems for the purpose of making the systems more directly responsive to the demands for service placed upon them. The present invention is directed to improved control apparatus for providing optimum service during periods of offpeak and down-peak operation, and also for providing controls which automatically shift the system to an off-hours program, and out of the off-hours program, in accordance with demands upon the system.

In accordance with the present invention, the system is always on an offpeak program if the traffic demands on the system are not such as to cause it to go into an up-peak, a down-peak, or an off-hours program. Certain traffic conditions automatically transfer the system from offpeak to downpeak, as will be described in more detail hereinafter; while absence of any demand for service for a predetermined period of time automatically shifts the system to an off-hours program. In addition, provision is made for an emergency" program in the event there is a failure of the normal means used to cause elevators to serve passengers at the various floors of the building served by the system.

In the customary, or offpeak mode of service, a normal terminal time" is established for departure of elevator cars from the bottom and top terminals served by the elevators. This is the time which ordinarily elapses from the selection of a car for dispatching from a particular terminal and the departure of the selected car from that terminal. Preferably a car is selected for dispatching only when there is a call for service. The normal terminal time at either terminal may be reduced in two different respects in response to certain demand conditions upon the system.

First, the dispatching interval is subject to modification dependent upon the ratio of building traffic in one direction to building traffic in the opposite direction. The ratio of traffic in the two directions is determined by accumulating the total time that elevator doors are open at intermediate floors for up traveling cars and for down traveling cars, during a given interval of time, and modifying the dispatching interval at one of the two terminals in accordance with the excess of accumulated door open time in one direction as against that in the opposite direction, the modification tending to restore imbalanced service in the two directions. If the cumulative door open time of up traveling cars exceeds that of down traveling cars the dispatching interval at the top terminal is shortened, and the amount by which it is shortened depends upon the extent of the difference between the up traveling cumulative door open time and the down travel cumulative door open time. Conversely, if the cumulative door open time of down traveling cars is greater than that of up traveling cars, the dispatching interval at the bottom is shortened.

Second, if the total amount of building traffic, as measured by the total quantity of up and down hall calls in simultaneous registration, exceeds a predetermined amount the terminal time at both terminals is reduced to a predetermined percentage of the normal terminal time. Conveniently, the reduction in terminal time based upon total building traffic shortens the terminal time to about 50 per cent of normal.

The first basis for modifying terminal timei.e., the cumulative door open time ratiocontinues to vary the dispatching interval at one or the other of the two terminals even when the normal terminal time has been reduced to one-half normal. The various possible terminal times will be hereinafter designated as follows:

l. The basic dispatch interval effective during the offpeak program is normal terminal time 2. The reduced dispatching interval based upon total building traffic will be referred to as reduced terminal time.

3. The reduction in either normal terminal time or reduced terminal time dependent upon the ratio of building traffic in opposite directions will be referred to as unbalanced terminal time."

It is apparent from the foregoing general description of the offpeak mode of operation of the elevator system that the system automatically accommodates itself to serve a high total volume of building traffic in both directions, and also accommodates itself automatically to any imbalance between traffic in the up direction and traffic in the down direction.

Comparison of cumulative door open time of cars traveling in the two directions requires that a comparison interval be established, and this interval is continuously recycled throughout the offpeak program. Conveniently, the door open times in the two directions may be accumulated for a comparison interval of seconds, and at the end of that time the terminal time at one terminal or the other is adjusted in accordance with the imbalance between the cumulative door open times at the end of the comparison interval. If there is no imbalance the two terminal times remain equal, either at the normal time or at the reduced terminal time. Assuming that an unbalanced door open time is established at the end of a first comparison interval, the unbalanced door open time remains in effect throughout the second comparison interval, and is then either retained or corrected in accordance with conditions at the end of the second interval, and so forth.

Likewise, the system requires that an interval be established for recording door open time, and'this is afforded by periodic pulses which are emitted from the time the door starts to open until it is fully closed. Thus, for example, if a door of an up traveling car remains open for 3 seconds it results in one pulse of the up car door open timer.

Selection of a proper comparison interval depends upon the number of elevators in a system, the number of floors in a building, the typical traffic patterns at different times of day, and other factors. Thus, the comparison interval is independently adjustable to permit the system to be modified, or tuned" in accordance with experience during the early stages of usage of the system.

Similarly, the pulse interval for counting up door open time and down door open time may be adjusted so as to coordinate the pulse rate with the comparison interval. l

Turning now to the down-peak mode of operation, a downpeak condition is considered to be in effect whenever any particular elevator car bypasses dowr. hall calls on two successive trips by reason of being loaded. For convenience such a bypassed hall call may be referred to as a load bypassed hall call.

Assuming the No. 1 car in the system load bypasses a down hall call on a first trip, and also load bypasses the same down hall call on the next succeeding trip, all load bypassed hall calls are established as preferred calls. The preferred calls may, of course, be answered by any available down traveling car i.e., any car which is not set to load by bass such call. if the No. 1 car in the system arrives at the first floor on the second of the above described consecutive trips, and at least one preferred service down hall call is in registration, the No. 1 car will then be selected for preferred servicje operation.

When a car is selected for preferred service operation, the following events occur: 1

1. Assuming that the system is a two car system, the second car will reverse at its highest call and return for immediate dispatch from the first floor.

2. In such a two car system, the second c r will also cause any down hall call which it load bypassesto be established as a preferred call. l 3. The preferred service car (i.e., the first car in this examminal.

4. The preferred service. car will reverse at the highest preferred call and serve only preferred calls below it until it becomes loaded, or until no further preferred calls are below it, at which time it will answer all down hall calls below it until it does become loaded. It will remain as a preferred service car until all preferred calls are served.

. .Only load bypassing of a down hall call by the selected preferred service car will establish that hall call as a preferred calli.e., a down service call registered after the establishment of preferred service does not become a preferred call merely because it is bypassed by the preferred service car, since the latter is conditioned to answer only preferred calls.

The establishment and termination of off-hours service also is dependent upon the demand for service upon the system. Initiation of the offhours program occurs, in general when there has been no demand for service on the system for a predetermined period of time. When any car has been idle for 6 minutes (or any other selected time period), herein called shut down time," the motor generator set for that car is auto matically shut down. When the motor generator sets of all cars are shut down, the system is automatically put on off-hours operation.

Assuming a two car system, the off-hours program is initiated when the second car shuts down its motor generator set. During offpeak operation of a two car system, one car ordinarily parks at the bottom terminal and one at the top terminal, each with its doors open, and a car is dispatched from either terminal only when there is a registered car call or hall call to be served by travel of the car toward the opposite terminal. When the shutdown time for the second car has expired, the car parked at the top terminal closes its doors and immediately starts to the bottom terminal, stopping to serve any registered down hall calls and car calls on the downward trip. The car parked at the bottom terminal remains there.

As the descending car arrives at the first floor its doors open to permit any passengers to depart; but no signals are actuated to indicate that the car is available for an up trip, the doors reclose, and the motor generator set shuts down as soon as the doors are fully closed. The car may respond to car calls registered by a passenger who happens to enter as the car arrives at the first fioor; but otherwise the car remains as a standby throughout the off-hours program. All building traffic is handled by the other, or operating car, which remains with its motor generator set shut down but with its doors open so that any passenger'approaching to go up will enter that car and press the car call button for the desired floor. This immediately starts the motor generator set, and after a set door open time the doors close and the car departs, answers all car calls and hall calls, returns to the bottom terminal and reopens its doors. After expiration of the shutdown time, the motor generator set again shuts down.

The off-hours program may terminate to return the standby car to service in response to any one of three conditions:

1. An off-hours timer begins to run each time the operating car leaves the bottom terminal, and is reset each time said car arrives back at said terminal. If the timer times out before the car returns to the bottom terminal, the off-hours program terminates. The timer may conveniently be set to permit the operating car to make a full round trip with a single stop in either direction, or such other predetermined time as suits the particular system and building.

2. Registration of a bottom terminal call, while the operating car is away from said terminal, conditions the offhours timer to time out at an expedited rate which may be less than half the usual period requiredi.e., seconds if the timer ordinarily times out in two minutes; and off hours program terminates.

3. Load sensing means in the operating car conditions it to bypass hall calls if the load exceeds a maximum, and if this occurs the off-hours program terminates immediately.

Emergency service is provided in the present system when, for example, there is a voltage supply failure to the hall call relays. Prior systems for providing emergency service have utilized means for registering false hall calls which would cause one car or another in the system to stop at every floor until the voltage supply to the hall call circuits was restored.

The present system includes an improved means for establishing emergency service which does not require the re gistration of false car calls.

The controller includes an emergency lane for each car having contacts which are energized when supply of voltage to the hall call relays fails. Such a controller lane is provided for each car in the system, and if all cars are in service the floors of the building are divided equally between the various cars so that each car stops at predetermined floors on any down trip during the continuance of the emergency condition. Thus, for example, in a two car system, one of the two cars may serve all odd numbered floors and the other car will serve all even number of floors. The energized contacts in each emergency program lane of the controller cooperate with the usual traveling controller contacts to cause the car to stop at the floor corresponding to the energized emergency program lanecontact. If one car is out of service, all emergency program contacts on the in-service car are energized so that the one car stops at all floors on each down trip.

Further features and advantages of the invention will readily be apparent from the following specification and from the drawings, in which: m

FIG. 1 is a diagrammatic illustration of an elevator which may be one of a multiple car elevator system;

FIGS. 2 and 2a are an across-the-line circuit diagram, partially diagrammatic, of circuitry associated with each car of the system;

FIGS. 3, 3a and 3b are an across-the-Iine diagram of control circuitry common to the two cars;

FIG. 4 is an across-the-line diagram of a portion of the hall call circuitry; and

FIG. 5 is an acrossthe-line diagram of a portion of the control circuitry associated with off hours or low demand operation; and 1 FIGS. 2', 2a and 3' and 3a, 3b, 4' and, 5 are keys for the corresponding across-the-line diagrams.

The detailed disclosure contained herein is limited for the most part to the novel circuitry of the invention. Detailed information on door operation, car speed controls, leveling and safety circuits, for example, are not shown. Any suitable control for providing the desired functions may be used.

Turning now to the drawings, FIG. 1 illustrates in diagrammatic form a single car 10 of an elevator installation. Car 10 is movable through a shaft 11 between a lower terminal floor 12 and an upper terminal floor 13. Intermediate floor 14 is representative of the several intermediate 1 vels in the building which may be serviced by the elevaton lvlovement of car 10 is effected by a variable speed motor 15 fenergized from a motor generator set 16. Motor 16a is preferably energized from a suitable three phase source (not shown) through a controller 17.

Elevator car 10 has a door 18 actuated by a suitable control mechanism 19.

The subsequent description contemplates an elevator system having two cars which travel between the lower and upper terminals serving a plurality of intermediate floors. Many of the novel features of the invention may be extended to systems incorporating three or more cars and to installations in which floors below the lower terminal, as basements, and above an upper terminal, as a penthouse, may be served.

The system has the normal or offpeak mode of operation in which one car will park at the lower terminal and the other at the upper terminal, each with its doors open and ready to receive passengers. The car at the lower terminal will be dispatched only if there is a demand for service, as a car call from a passenger entering the car at the terminal or an up hall call, or if the top termin'al parking requirement is not filled or about to be filled by an up traveling car. Similarly, the car at the upper terminal will be dispatched to answer a car call, a down hall call or to fulfill the lower terminal parking requirement. Dispatching interval timers at each terminal control the period of time a car must wait at a terminal before leaving for the other terminal or to answer a call.

In the following discussion the two cars of the system will be designated a and b; and certain components individual to the cars will be indicated by the appropriate suffix 0" or b, where such indication will aid in an understanding of the operation of the system. In some cases, contacts are shown for relays which are not illustrated. The conditions under which these relays are energized will be described, although the circuits for them may not form an essential element of the invention.

Turning now to FIG. 2 of the drawings, a portion of the control circuits for one car is illustrated. Lines 20 and 21 are connected with a source of-operating potential, as 110 v. AC. Block 22 represents suitable car running, leveling and door operator controls, the details of which form no portion of the invention. Certain elements of these controls are illustrated within box 22, as an aid to an understanding of other operations of the control circuitry.

A car at a terminal will be conditioned to run by energization of signal-for-up-direction or signal-for-down-direction relays SUA and SDA, each of which has a contact in the circuitry of the car running controls 22. When the car is parked at the lower or upper terminal, during off peak or normal operation, neither relay SUA nor SDA is energized.

The operation of the circuits for dispatching a car upwardly from the lower terminal will be considered first. The energization circuit of signal-for-up-direction relay SUA includes contact SDA-2 which is closed except when the car has been selected for down operation (as to a basement), contact NU-al of the next-up relay NU-a, which will be closed as described below, contact NUT, associated with the next-up timer NUT, contact CU-I associated with the up call relay, closed when an up call is registered, and contact UTZ-l, closed except when the car a is at the upper terminal. A holding circuit for relay SUA is completed through contact SUA-2 maintaining the signal for up direction once it has been established, until the car reaches the upper terminal and contact UTZ-l opens.

Next up relay NU-a has an energizing circuit including contacts PL which are closed when the car is at the lower terminal and in service, normally closed contact Oil-4 associated with the off hours relay OH and contact NU-bl associated with the N U-b relay for the car b. Whenever car a arrives at the lower terminal and is in service, assuming that off-hours operation is not in effect, and that the other car, b, has not been selected for up operation, relay NUa is energized. In the circuitry for car b, a similar circuit for relay NU-b (not shown) is interlocked with relay NU-a.

Turning now to the common signal schematic, FIG. 3, which shows circuits common to all cars, the basic operation for the lower terminal dispatching interval timer NUT will be described. The lines 25 and 26 are connected with a suitable source of power, as 110 volts AC. Timer NUT, connected across the line includes an electronic timing circuit and a relay NUT which is energized on expiration of the timing period. The details of operation of the circuit are not necessary to an understanding of the system operation. An enabling circuit for the timer is connected between terminals 28 and 29 and must be completed before the timing period starts. The dispatching interval may be reduced by changing the resistance across'terminals 30 and 31, in a circuit with the internal resistance of the timer (not shown).

The operation of timer NUT is initiated by closing of either contact NU-a2 or NU-b2 to complete the circuit between terminals 28 and 29. Contact 0H2 is closed in ofi-peak operation. It will be recalled that relay NU-a or NU-b closes when the respective rar is at the lower terminal, available for dispatch and the other car has not already been selected as next to be dispatched in the up direction. A suitable dispatching interval, as 15 seconds, may be selected for the usual operation of the timer. At the end of the timing period, contact NUT closes, in the circuit of relay SUA (FIG. 2). If there is no up call registered, relay SUA is not energized and the car is not dispatched. Upon registration of a service call closing contact CU-l, or if CU-l is closed when NUT closes, relay SUA is energized, closing contact SUA-1 in the car controller 22 and initiating operation of the door operator and car running circuitry. The car leaves the lower terminal to answer registered car calls and up hall calls, proceeding to the upper terminal.

The down car selection and dispatch circuitry is similar and will be described only briefly. Signal for down direction relay SDA (FIG. 2b) is energized through interlock contact SUA-3, next down relay contact ND-al, down dispatch'timer contact NDT, down call contact CD-l and contact LTZ-al, indicating that the car is not at the lower terminal. A holding circuit is completed upon energization of relay SDA through contacts SUA-3, SDA-3 and LTZal.

Next down signal relay ND-a has an energizing circuit including contact PT which closes when the car a is at the upper terminal, and an interlock with relay ND-bl, preventing the car a from being selected at a time when car b has already been selected. The upper terminal dispatching interval timer NDT is identical with the timer NUT. It is energized by connection between lines 25 and 26 and operation is initiated upon completion of the circuit between terminals 35 and 36, upon closure of either contact N D-a3 or ND-b2, the next down signal relays for the two cars. The basic timing interval, as 15 seconds, for the timer NDT may be varied by changing the resistance across terminals 37 and 38. Upon closure of contact NDT, relay SDA is energized, closing contact SDA-1 in the control circuitry 22 initiating the closure of the doors and downward movement of the car.

In accordance with the present invention, the period of operation of the timers NUT and NDT is varied as a function of the demand for service in the system. More particularly, the dispatch interval times are varied in accordance with the difference between the door open time for up traveling cars and the door open time for down traveling cars. Information regarding the door open times is accumulated for a predetermined period, as seconds, and then utilized to modify the operation of the appropriate dispatch timer. For example, if the door open time for up traveling cars exceeds the door open time for down traveling cars during the measuring period, the dispatching interval at the upper terminal is reduced while that of the lower terminal remains unchanged. Similarly, if the door open time for down travel cars exceeds that of up traveling cars, the dispatch interval at the lower terminal is reduced. This reduces the tendency of a car whose doors are open for an extended period during travel between the terminals to lag behind the other car in being dispatched from the terminals. In addition, the overall traffic in the system is measured and when it exceeds a predetermined quantity, both dispatch intervals are reduced by a predetermined factor, as one-half.

The operating time for the terminal dispatching interval timers NUT and NDT is reduced by introducing resistance between terminals 30 and 31 of timer NUT or terminals 37 and 38 of timer NDT. Associated with timer NUT are two step switch sections STP1-3 and STP2-3 connected to terminals 30 and 31 through contacts STSR-l and STSL-l of the right and left step switch relays STSR and STSL, respectively. These relays are energized alternately, as will appear, to connect one or the other of the step switch sections STPl-3 and STP2-3 with the timer. The circuitry for operating the step switch sections will be discussed below. For present purposes it is sufficient to understand that the movable contacts of the switches will be displaced from the center or home position, in which they are shown, in a counterclockwise direction if the door open time for down traveling cars exceeds the door open time of up traveling cars, while displacement will be in the clockwise direction ifthe door open time of up traveling cars exceeds that of down traveling cars. Each of the step switches has 12 positions in each direction from the home position. Connected between the terminals located in a counterclockwise direction from the home position of switch STPl-3 are series of resistors 39. When switch STP1-3 is in its home position or any positionto the right thereof, all of the resistance is connected in the circuit. The total resistance is a portion of the circuitry which establishes the basic second operating time of timer NUT. As the movable contact of switch STP1-3 moves in a counterclockwise direction, the resistance connected across terminals Bib-31 of timer NUT is reduced until at the end of travel of the movable arm, there is no resistance connected in the circuit and a short appears across terminals 30-31. This corresponds with a dispatch interval time of 0 seconds.

If the door open time of up traveling cars exceeds-that of ,down traveling cars, the movable arm of step switches is displaced to the right of the home position and the timing interval of timer NUT is not reduced.

- To minimize the number of physical resistors in the circuit, connections are made between terminals of stepswitch section STP2-3 and the correspondinggterminals of switch section STPl-3. Accordingly, no matter which switch section is operative, it ist he same resistors which are connected in the circuit.

. for up traveling cars exceeds that for down traveling cars, step switch STPl-2 or STP2-2 is displaced in the clockwise direction shorting a portion of resistors reducing the resistance connected across terminals 37-38 of timer NDT. Again, the number of physical resistors used is minimized by connecting appropriate terminals of switch section STP2-2 to corresponding terminals of STPi-2, as indicated in H6. 3a.

During the time that one of the step switches is controlling the operation-of timers NUT and NDT, as switch sections STPI, information regarding the relative door open times for the cars is accumulated by step switch STP2. At the end oithe timing period, the operation is reversed with switch sections S TPZ controlling the operation of timers NUT and NDT, and information being accumulated by step switch STl-l. The circuitry which affects this operation will now be described in detail.

Each car is provided with a door switch (part of controls 22, FIG. 2), which closes when the door of the car is not fully closed, energizing relay DCIJ. This in turn closes contact DCL-l (FIG. 2a). if car a is not at one of the terminals, both contacts UTZ-Z and LTZ-aZ are closed and one of the up or down door open signaling relays UX-a or DX-a, respectively is energized depending on the direction of travel of the car as indicated by the closure of contact SUN-4 for up travel or SBA-4 lf thc car is conditioned for travel in the down direction.

The up and down door timers UDT and DDT (FIG. 30) proas will appear. Timer UDT operates only when one or both of resistors 43 and 44 is connected between terminals 45. 46. Connected in series with resistor 43 is contact UX a associated with the up door open signal relay LIX-11 for car a while resistor-44 is connected across terminals 45 and 4a through contact UX=b associated with the up door open signal relay for car 12, Thus, whenever a car conditioned-for up travel is stopped with its doors in' other than the fully closed position, one of resistors 43 or 44 is connected in the circuit of timer UDT. If both cars are moving in the up direction and are stopped with their doors in other than the fully closed position, both resistors 43 and 44 are connected in the circuit. The period of timer UDT is such that with one of resistors 43 or 44 connected in the circuit, it will time out in a period of 3 seconds. With both/resistors connected in the circuit the timing period is 1% seconds. As will appear, timer UDT is automatically recycled and the rate at .which it times out, i.e. the rate of energization of relay UDT, provides a measure of the total door open time of up traveling cars.

Timer UDT is recycled in the following manner. Capacitor relay UDTR and relay TUDT are both normally energized and their respective contacts UDTR and TUDT are closed. When timer UDT times out energizing relay UDT, contact UDT-l opens. Capacitor relay UDTR is immediately deenergized, opening its associated contact UDTR. Relay TUDT provides a slight delay in dropping out to permit relay UDT to be picked up for a short interval of time in order that the variouscon- -tacts associated therewith will have an opportunity to perform their functions. When relay TUDT times out, contact TUDT associated therewith opens dropping out relay UDT, whereupon contact UDT-l closes energizing capacitor timer UDTR which picks up after a slight delay. Following this delay,-contact UDTR closes reenergizing relay TUDT and reestablishing the enabling circuit for UDT.

Down-door open timer DDT operates in a similar manner as up-door-open timer UDT. In offpeak operation, contact OP-2 is closed completing the timer actuation circuit between terminals 47 and 48 through reset contact TDDTlAny time a car conditioned for down travel is stopped and its doors are not fully closed, one or both contacts DX-a and DX-b is closed, connecting one or both resistors 49 and 50 across terminals 5!, 52. The timing rate of timer DDT is the same as that for UDT, 3 seconds with one resistor in the circuit and 1% seconds with both. The reset circuitry for timer DDT is identical with that for timer UDT and a specific illustration and description of it is not given. The rate of actuation of relay DDT provides a measure of the door open time of down traveling cars.

interval timer IT provides a time base for the measurement of door-open time, controlling the period during which information is collected by the' step switches. During offpeak operation, contact OP-3 is closed completing the actuating circuit of timer IT through closed contact TIT associated with a reset circuit for the timer. A suitable operating period for timer IT is seconds. The reset circuit for timer IT is identical with that provided for timer UDT and a specific disclosure and description are not given.

Energization of relay IT at 90 second intervals closes contact IT momentarily energizing step switch relay S'IS. Relay STS is a single coil impulse latching relay similar in operation to a toggle switch. it has associated therewith two contacts STS-L and STS-R, one of which is closed at all times energizing the corresponding relay STSI. or STSR. Upon each actuation of relay STS by timer IT, the condition of contacts STS-L and STS-R is reversed, reversing the condition of relays STSL and STSR and establishing which of the step switches STPl and STPZ collects information or controls timers NUT and NDT.

For the purpose of the immediately following discussion, it will be assumed that contact S'lS-L is closed, energizing relay STSL. Considering now the actuating circuitry for step switch STPI (FIG. 3b), it will be seen that contacts STSL-il and STSL-4, associated with left step switch relay STSL, complete energizing circuits for step switch stepping coils STPi (up) and ST?! (down), respectively. Included in the energizing cirsuits for these stepping coils are contacts UDT-2 and DDT-2, respectively, which are associated with the door open timers UDT and DDT. Upon each actuation or recycling of the dooropen timers. an impulse is transmitted to the appropriate up or down stepping coil. This causes a stepping motion of the movable arm of step switch STPl in either the up or down v direction.

During the time door-open information is transmitted to the step switch STPl, the timers NUT and NDT are under the control of step switch STPZ as contacts STSL-l and STSL-Z (FIGS. 3 and 3a.) are closed.

At the end of the period of timer IT, contact IT closes, pulsing relay STS and reversing the condition of contacts STSL and STSR. Contact STSR closes, energizing relay STSR while contact STS-L opens breaking the circuit for relay STSL. This results in disconnecting step switch sections STP2-2 and STP2-3 from timers NDT and NUT, and connecting step switch sections STPl-Z and STP1-3 thereto. Contacts STSL-3 and STSL.-4 open, preventing the transfer of further door open information to step switch STPl while contacts STSR-3 and STSR-4 close directing door open information to step switch STP2.

At the end of each 90 second period of timer IT, the step switch which has just finished controlling the operation of timer NUT and NDT is reset before further information is transmitted to it. On closure of contact IT, an energizing circuit is completed to capacity timer TSRS (FIG. 3a). This timer does not complete its cycle and actuate the contacts associated therewith for a period of approximately one-half second. This delay insures complete transfer of relays STSR and STSL. Relay ITS, in parallel with relay STS and timer TSRS, is energized on closure of contact IT, closing holding contacts ITS to a circuit including step switch homing relay contacts STPIH and STPZI-I. Upon completion of the period of timer TSRS, a circuit is completed through contact TSRS-l and contact STSR-5 to the movable arm of step switch STP2-l (FIG. 3b). Unless the movable arm of the switch is at the center or home position, the up-step coil STPZ (up) is energized through interrupter switch STP2. The interrupter switch opens and closes automatically providing impulses to the step coil moving the arm of switch STPZ-l in the clockwise direction until it reaches the home position (in which it is shown) at which time a circuit is completed through contacts TSRS-l and STSR-5 energizing homing relay STPZH. Energization of this relay opens contact STPZI-I in the holding circuit for timer TSRS dropping it out, opening contact TSRS-l and closing contact TSRS-2. This completes the homing operation and step switch STPZ-l is ready to accept further door-open information through the action of timers UDT and DDT, and contacts UDT-2 and DDT.

At the end of the next 90 second period of timer IT, the two stepping switches STPl and STPZ will reverse their functions, with STP2 controlling the operation of timer NUT and NDT and STPl again collecting information on door-open timers (after having been reset at the home position).

It will be noted that during the homing operation, contact TSRS-2 is opened, preventing the completion of the circuitry to the stepping coils through the door timer contacts UDT-2 and DDT.

Whenever the system is in other than the offpeak mode of operation, contacts OP-4 and OP-S close causing both the step switches STPl and STP2 to seek the home positions.

The timing period for timer IT must be selected to provide the proper corrective operation depending upon the nature of the elevator installation. If the installation is subject to rapid shifts in the nature of the service demand, the period of operation of timer IT should be relatively short. On the other hand, if the changes are more gradual, the period may be longer. The timing periods for timers UDT and DDT should be quite short as compared with the base time of timer IT.

The basic operating time of the terminal dispatch interval timers NUT and NDT may be varied in accordance with the total number of service calls registered in the system. A quota relay, QA (FIG. 3b) performs this function. Rectifier 60 provides a direct current operating potential, stabilized through a voltage regulator 61 for the relay QA. Relay QA is energized through a circuit including potentiometer 62 and normally provided, representing the up and down calls registered for each floor in the system, it being understood that there is a U- contact and D-contact for each floor corresponding to the hall calls which may be registered. When a sufficient numberof n U or n D contacts is closed to effect energization of relay QA, contact QA-l opens introducing potentiometer 63 into the circuit which may be adjusted to control the dropout point for relay QA. Contact QA-2 (FIG. 3) closes connecting resistor 64 across terminals 30 and 31 of timer NUT. This reduces the timing period by a predetermined factor, as one-halt. For example, in'a specific installation, timer NUT has a period of 15 seconds without resistor 64, but with all of the resistors associated with step switch STPl-3 in the circuit. The addition of resistor 64 reduces this time to 8 seconds. The step switches still continue to modify this time as required by the relative up and down door-open time of the cars. Similarly, contactQA-3 connects resistor 65 in the timing circuit of timer NDT when the predetermined number of calls is registered. During periods of up-peak operation, contact UPK is closed connecting resistor 64 in the circuit of the lower terminal dispatching interval timer NUT.

In the event of a failure in the voltage supply for the hall call pushbuttons, it is desirable to provide a means for conditioning one or both cars to stop at the various floors of the building to pick up passengers who may be waiting. It has in the past been proposed to accomplish this through the synthetic registration of service demands. This requires complex circuitry and necessitates the energization of a substantial number of relays. The present system provides for emergency service by conditioning the car or cars in operation for stopping at each or alternate floors, in a novel manner.

A portion of the hall call circuitry is shown in FIG. 4, obtaining its energization through lines 66 and 67, from a suitable source. When the lines are energized, relay CPF, connected thereacross, is energized, closing contacts CPF-l and CPF-2 to the remainder of the circuit and opening contacts CPF-3 and CPF-4. Should the hall supply voltage fail, relay CPF drops out opening contactsCPF-l, CPF-2 and closing contacts CPF-3, CPF4. An attempt is made to recover power for the hall call circuitry from the elevator cars. If voltage is available from car a, relay PFA is energized closing contacts PFA-l and PFA2, opening contacts PFA-3 and PFA-4. As contacts CPF-3 and CPF-4 are closed, voltage from the car a in the hall call circuit may be utilized. If voltage is not available from car a, relay PFA is dropped out with contacts PFA-l, PFA-Z open and contacts PF A-3, PFA-4 closed. This permits voltage which may be available from car b to energize the hall call circuitry. If, however, voltage is not available from either car, due to broken connections or to blown fuses 68, 69, relay CF F is not energized.

Contact CFF (FIG. 2a, below broken line 70) is closed completing an energization circuit for emergency relay 2EP. If both of the cars a and b are in service, only relay 2B? (for each car) will be energized. If, however, one of the cars is out of service, the interlock relay contact SS-b, for example, will be closed completing an energization circuit for relay lEP-a. If car a is out of service, a similar relay lEP-b is energized through interlock contact SS-al in the individual circuitry for car b. A portion of the car call circuitry is illustrated in FIG. 20, below broken line 71. Before proceeding with a consideration of the emergency operation, a brief description of the normal operation will be given.

The circuitry for one floor, n, is shown. It will be understood that similar circuitry will be provided for each of the floors to be sewed. When a car call is registered as by pressing a pushbutton n in the car, relay n C is energized and contact n C closes completing a holding circuit. At the same time, an operating potential is applied to fixed segment n CC, a part of the car position mechanism. The brushes CC] and CC2 are part of the car position mechanism and move relative to the fixed segment n CC in accordance with movement of the car. Depending upon the direction of the travel of the car, either 

1. In an elevator system having: a shaftway serving a plurality of floors including a bottom terminal floor, several intermediate floors, and a top terminal floor, a plurality of elevator cars in said shaftway to serve said floors, means for dispatching each of said cars from either terminal floor on trips up and down said shaftway at a predetermined terminal time after a selected occurrence, including separate timing means for each terminal floor, a door at each of said plurality of floors for access to each of said cars, call means at each floor and within each car for registering calls for service, means responsive to operation of the call means for causing each car to stop on up trips and on down trips at any intermediate floor as to which a call for service is registered which requires travel in the direction the car is moving, and door operating means associated with each car for opening and then closing the door at each floor at which the elevator stops, the improvement which comprises: means for balancing against one another the total of all door open time on up trips and on down trips; and means for adjusting the terminal time at a terminal floor in response to an imbalance between up door open time and down door open time, to establish a shorter time at the terminal toward which traveling cars have an excess of door open time, than at the other terminal, to compensate for such imbalance and maintain substantially equal spacing among cars in the system.
 2. The system of claim 1 which includes means providing a comparison time interval during which the up trip door open times and down trip door open times are continuously balanced against one another, and dispatch control means operable at the end of the comparison time interval to adjust the terminal time.
 3. The system of claim 2 which includes means for adJusting the comparison interval.
 4. The system of claim 1 in which the adjusting means includes means for adjusting terminal time in increments, and in which the number of increments of adjustment applied at any one time is proportional to the degree of imbalance then existing between up door open time and down door open time.
 5. The system of claim 4 in which an excess of up door open time reduces the terminal time at the top terminal.
 6. The system of claim 4 in which an excess of down door open time reduces the terminal time at the bottom terminal.
 7. The system of claim 1 which in addition includes means for determining the total demand for service in both directions, and means responsive to a maximum level of total demand for reducing the terminal time equally at both terminals.
 8. The system of claim 7 in which the means for determining the total demand comprises means for measuring the total number of up and down calls in simultaneous registration from the call means at all the floors.
 9. The system of claim 7 in which the adjusting means is arranged to adjust terminal time at either terminal from the normal terminal time and also from the reduced terminal time, toward zero.
 10. The system of claim 1 which includes means responsive to the opening of a door at an intermediate floor for producing cyclic pulses until the door closes, means for continuously balancing pulses produced during up door open time against pulses produced during down door open time, and dispatch control means operable at the end of an established comparison time interval to adjust terminal time at either of the terminal floors.
 11. The system of claim 10 which includes means for adjusting the time between pulses.
 12. The system of claim 2 wherein said dispatch control means includes first and second means for adjusting the terminal time, each responsive to said comparison time interval means for alternately balancing up trip and down trip door open times and adjusting said terminal time, said first means balancing the door open time while the second means controls the terminal time, and the second means balancing the door open time while the first means controls the terminal time.
 13. The system of claim 12 including an electronic dispatching timer and circuit means having a plurality of portions for establishing different terminal times, said first and second terminal time and adjusting means including first and second multiple switching means, actuable from position to position to balance the door open times and to select the corresponding circuit means portion to establish the time of said electronic dispatching timer. 